1. Field of the Invention
This invention relates generally to current limiting fuses and more particularly to fuses having means for shaping and controlling the arc voltage developed by the fuse during high current interruptions.
2. Description of the Prior Art
Current limiting fuses presently employed in rotating rectifier equipment are routinely subjected to a variety of mechanical and electrical stresses during normal operation. These stresses operate on the notched portion of the fuse element in such a way as to cause premature and undesirable opening of the fuse, resulting in loss of service and possible expensive equipment failures. It would, therefore, be desirable to eliminate the notches or restricted areas from fusible elements of fuses operating in this equipment. Notches are conventionally provided in the fuse element of current limiting fuses to control and limit the fuse arc voltage generated during fault current interruption. Elements of uniform cross section, such as wires, unnotched strips and the like, lack this control feature and are capable of generating arc voltages high enough to cause insulation failures in associated equipment.
From an interruption standpoint, the ideal arc voltage shape would be rectangular. That is, it would instantaneously rise to a fixed, predetermined level and remain there until current extinction was assured, at which time it would then drop to zero.
It would be desirable if a fuse design were available that exhibited the arc voltage control characteristics of the traditional notched fuse element design and were capable of withstanding the mechanical and electrical stresses associated with rotating rectifier equipment by the use of rigidly supported uniform fusible elements.